Nick - Professional High Bodies could have either squad benches or jump seats - my '67 has the bench, of my 3 '76s, two have jump seats, one has a bench.
Kurt - as Nick said, the full width flooring doesn't negate having a squad bench - in removing the bench in my '67, I can attest that the flooring runs fully underneath the bench, and the interior is fully trimmed out in vinyl behind the bench - if you remove the bench, the only thing you would notice is the screw holes in the floor.
I would say that placement of the rear in-floor compartment door does indicate a bench, but you should see some screw holes in the floor if that were the case.